Collapsible real-time session stats panel (tokens, context, API calls, premium requests, cache, duration)

[berrat]

Describe the feature or problem you'd like to solve

There is currently no way to monitor session resource usage at a glance during an active session. To understand how much context has been consumed, how many API calls have been made, or how many premium requests have been used, a user must either wait for a crash/compaction or dig through logs after the fact. For power users, teams on metered plans, and anyone running long or expensive sessions, this lack of real-time visibility is a significant gap.

Proposed solution

Add an optional Session Stats panel — collapsible/expandable, togglable via config — that renders a live compact summary of resource and performance metrics for the current session.

Folded (compact, one-line):

📊 Stats  ctx 68%  ↑42k/↓18k tok  🕒 12m 34s  calls 37  premium 8

Unfolded (expanded):

📊 Session Stats
  Context          68% used  (87,040 / 128,000 tokens)
  Tokens sent      42,310
  Tokens received  18,045
  Cached tokens    11,200  (21% of sent)
  API calls        37  total  (28 standard · 8 premium · 1 cached)
  Premium requests 8
  Duration         12m 34s
  Avg. turn time   ~20s

Suggested stats to surface:

Stat	Description
Context usage	Current fill % and absolute tokens vs. window size
Tokens sent	Cumulative input tokens for the session
Tokens received	Cumulative output tokens for the session
Cached tokens	Tokens served from prompt cache (where applicable)
API calls	Total LLM requests, broken down by standard / premium / cached
Premium requests	Count of premium-model calls against plan quota
Session duration	Wall-clock time since session start
Avg. turn time	Average time per agent turn

Controls:

• Toggle fold/unfold: a dedicated keyboard shortcut (the specific key should avoid conflicts — e.g. Ctrl+S sends XOFF in some terminals and should not be used; a safe alternative such as a function key or a free modifier combo should be chosen) or by clicking the panel header
• Opt-in via config.json:

  { "statsPanel": true }

• Fully disabled by default to preserve a clean UI for new users; power users explicitly enable it.
• Stats persist and accumulate across compaction events so the total is always session-wide, not just the current context window.

Example prompts or workflows

1. User on a metered Copilot plan monitors premium request count in real time — knows at a glance when they're approaching their quota before the session ends.
2. Long refactor session running for 45 minutes: user glances at the folded one-liner to see context is at 72% and decides to manually /compact before it auto-compacts.
3. User notices cached token % is low and adjusts their workflow to reuse more context, reducing cost.
4. Team lead shares a screenshot of the expanded stats panel with their team to communicate session cost and complexity.
5. User keeps the panel folded for minimal UI footprint — the single-line summary gives just enough signal without cluttering the screen.

Additional context

• OS: Windows 11 Pro (Build 26200 / 24H2)
• Shell: PowerShell 7.5.4
• Copilot CLI: 0.0.420 (win32-x64)
• The /context command already surfaces context usage — this panel extends that concept to a persistent, live, multi-metric view accessible without leaving the main session flow.
• The collapsible panel pattern is already established in the TUI (checkpoints, MCP, context) — this fits the same model.
• Stats should survive context compaction and reflect true session totals, not just the current window's figures.